In general machines are adjusted into a horizontal position which is required or desirable for trouble-free operation thereof, by means of a plurality of levelling shoes and anchor bolts which are respectively associated therewith. As however the weight distribution of machines of that kind is frequently not uniform but sometimes varies widely, massive, large and thus expensive levelling shoes need to be used only at heavily loaded locations, while smaller and thus less expensive levelling shoes can be employed at less heavily loaded locations. The use of different levelling shoes however frequently gives rise to the problem that the height adjustment range available in the case of smaller levelling shoes may not sufficient.
When using conventional levelling shoes with a relatively large flat support surface which is for example square or rectangular, height compensating plates can be inserted in order to increase the height adjustment range. The insertion of height compensating plates of that kind with one or more through bores for the anchor bolt or bolts, however, requires dismantling the levelling shoe or removing the levelling shoe from the supported machine, which is time-consuming and consequently disadvantageous. If slotted intermediate sheet metal shim or spacer members are used instead of the height compensating plates which have through holes, precise levelling is not guaranteed because for example the protruding edge flange configurations which are produced upon stamping of such members mean that flat surface contact thereof is not guaranteed. In addition it is possible for intermediate sheet metal shim or spacer members of that kind to slip out during operation, which increases the susceptibility to trouble and has an adverse effect on operational safety. The described height compensating plates with through holes or the slotted spacer members can also be used with levelling shoes with a support ring arranged on the top side thereof, but they suffer from the same disadvantages in principle as in the case of levelling shoes with a large-area support surface. Levelling shoes of that kind with a support ring are however advantageous in particular if on its underside the support ring is in the form of a portion of a sphere and the corresponding contact surface of the levelling shoe is of a complementary configuration thereto in order to permit inclined adjustment of the supported machine or precise horizontal orientation thereof when the floor is inclined, as is indispensable for stress-free precision levelling.